Air filter for compressed air systems



n 19 A. E. SCHMIDLIN 2,531 94 AIR FILTER FOR COMPRESSED AIR SYSTEMSFiled May 8, 1947 2 Sheets-Sheet l mmml IIIIIM IN V EN TOR. Algensl BYATTORNEY A. E. SCHMIDLIN 2,537,094

AIR FILTER FOR COMPRESSED AIR sYsTEMs :2 Sheets-Sheet 2 Jan. 9, 1951Filed May 8, 1947 IN V EN TOR.

A/Zenzs iizzz/k agk ATTORNEY Patented Jan. 9, 1951 UNITED STATES TENTOFFICE AIR FILTER FOR COMPRESSED AIR SYSTEMS Application May 8, 1947,Serial No. 746,829

8 Claims.

The present invention relates to compressed air systems, and, moreparticularly, relates to air filter means for such systems.

The present invention is applicable to com pressed air systems whereinthe compressor is driven continually and the compressed air is stored ina receiver but is used only from time to time. In order to maintain thestored air at a predetermined pressure in such a system, bypass meansare provided for venting the compressed air supplied by the compressorto the atmosphere when the stored air attains a pre determined pressurevalue and for again supp ing air to the receiver when the pressuretherein falls to a predetermined value.

The present invention is directed to a compressed air system of theforegoing type wherein filter means are provided for filtering the airdo livered from the exterior to the intake of the compressor and theby-passed compressed air is supplied to the intake of the compressorwhen the stored air in the receiver attains a predetermined pressurevalue.

Accordingly, an object of the present invention is to utilize theby-passed compressed air for cleaning the filter means.

Another object is to provide a blast of air for removing dirt particlesfrom the filter means to reactivate the same.

Another object is to direct lubricating oil carried by the compressedair against the filter means to facilitate cleaning of the filter means.

Another object is to conserve the supply of lubricating oil byrecirculating the by-passed air carrying oil picked up during itscompression.

A further object is to provide apparatus for accomplishing the foregoingobjects and advantages.

Other and further objects of the invention will be obvious upon anunderstanding of the illustrative embodiment about to be described, orwill be indicated in the appended claims, and various advantages notreferred to herein will occur to one skilled in the art upon employmentof the invention in practice.

In the drawings:

Figure 1 is a schematic view of a compressed air system embodying thepresent invention.

Figure 2 is a fragmentary enlarged view of the compressor, partly insection and partly in elevation, illustrating the filter means and themeans for reactivating the same.

Figure 3 is a sectional view taken along the line 3-3 on Figure 2.

Figure 4 is an, enlarged longitudinal sectional View illustratingby-pass control means.

Figure 5 is a schematic view of a modified com- 2 pressed air systemembodying the present invention.

Figure 6 is an enlarged longitudinal sectional view illustratingmodified by-pass control means adapted to be utilized in the systemshown in Figure 5.

Referring to Figure 1 of the drawings, there is shown an air compressorIt of the multi-stage type herein illustrated as a radial compressorhaving first, second, third and fourth stages ll, I2, l3 and M,respectively. The outlet of the first stage is connected to the inlet ofthe second stage by a conduit I5 provided with an intercooler I6 and avalve 21; the outlet of the second stage is connected to the inlet ofthe third stage by a conduit I! provided with an intercooler iii; theoutlet of the third stage is connected to the inlet of the fourth stageby a conduit [9 provided with an intercooler 2i]; and the outlet of thefourth stage is connected to a receiver or reservoir 2| for thecompressed air by a conduit 22. The contents of the receiver are adaptedto be dispensed through a discharge valve 23 in a conduit 24 connectedto the receiver. The arrows applied to the conduits illustrate thedirection of the flow of the air therethrough.

Air from the atmosphere is adapted to be supplied to the inlet of thefirst stage through a filter assembly 25 (Figures 2 and 3) and by-passedcompressed air is adapted to be supplied to the inlet by a conduit 26connecting the interior of the filter assembly to the conduit 15 b meansof the valve 21 which is controlled by pressure operable means 28(Figure 4) connected by a conduit 29 to the conduit 22.

As shown in Figure 4, the valve 27 comprises a body having a chambertherein provided with an inlet 30 and an outlet 3! for connection in theconduit I5, and a by-pass outlet 32 for connection to the conduit 26. Avalve seat 33 is formed between the inlet 30 and the outlet 3! and avalve seat at is formed between the inlet 36 and the outlet 32. A valvemember 35 for the seat 34 normally is retained thereon by a spring 36and a valve member 3 for the seat 33 connected for movement with thevalve member 35 normally is retained in unseated position and isarranged so that it is seated upon unseating of the valve member 35.

This operation is adapted to be effected by the pressure operable means28 comprising a body connected to the valve body and having a chamberprovided with an inlet 38 to which th conduit 29 is connected, a snapaction diaphragm 39 in the chamber responsive to the pressure of the airadmitted through the inlet 38, and a stem 36 gonnected to the diaphragmand the valve mem- The filter assembly 25, illustrated more particularlyin Figures 2 and 3, comprises a caplike casin 44 mounted over the intakeports 43 in the head 45 of the first stage cylinder, and an absorbentair filter element 46 positioned Within the casing.

The casing 44 comprises a circular top wall 41 provided with a centralaperture 49, and a cylindrical depending skirt or side wall 50 providedwith a plurality of circumferentially spaced air inlet apertures 51 andhaving its lower edge turned inwardly and upwardly to form an annulargroove 52. The filter element 46 is supported between a pair ofdisk-like screens 54 each having a top wall 55 adjacent the underside ofthe top wall 4'! of the casing provided with a central aperture 56 andeach having an arcuate downwardly and outwardly extending side wall 51'terminating in a free edge 59 seated in the annular groove 52. Thefilter element conforms to the shape of screens 54 and has a centralaperture 69 in alignment with the aperture 49 of the casing 44 and theapertures 56 of the screens 54.

The filter assembly is removably secured to the cylinder head 45 by abolt 5|, or the like, extending through the apertures 49, 56 and 6!! andscrewed into a threaded aperture 62 of the head.

In order to clean or reactivate the filter element 46, a substantiallyannular tube 65 is mounted on the cylinder head 45 underneath andadjacent to the arcuate side wall 54 of the inner screen. The tube 65has a plurality of circumferentially spaced upwardly facing apert res asfor direct ng compressed air against the fi ter el ment. The tube isconnected in fluid flow communication with the conduit 26 by a dependingtube portion 61 thereof which is secured in one end of a passage 69formed in the cylin r h ad and has the conduit 26 secured in its otherend.

In operation, wh le the pressure of the air in the receiver 2| is belowa predetermined value, the pressure operable means 28 maintains thevalve members 35 and 31 in seated and unseated po ition, re p cti ely,whereby the air compressed in the first stage I! flows bv wav of the inlt *0, th out et 3! and the conduit IE to the intake of the second tage.Air is admitted to the intake ports 3 of the fir t tage throu h thea.nert"1' s 5! n t e casing 44-. the filter element 46 and its sup ortinscreens 54.

Wh n a pr determined pressure has been est bl shed in the recei er, thepressure operable means 28 effects sudden un eatin of the valve m m er35 and seatin of the va ve member 3?, whereb air com ressed in the firststa e is b pa sed through the valve 21 by way Of the inlet 39 an the outet 32 and is conducted by the conduit 26 to the d trib tin tu e 65 whichdirects it a ain t the filter element 46.

Th bv-Dassed compr ssed air directed against the filter element iseffective to blow out dust, dirt or other foreign particles which havecollected on the filter element wherebv the filter element is cleaned toincrease the life of its effective use. At the commencement of theunloading phase, the rate of flow of by-passed air exceeds the intakerate of the first sta e due to release of compressed air stored in theintencooer Hi. This effect provides a sudden blast of air wh ch has ahighly efficient cleaning action on the filter.

Also, the by-passed compressed air picks up lubricating oil from thefirst stage of compression and portions of this oil are absorbed by thefilter element to further reactivate its dirt catching properties. Sincea substantial portion of the by-passed air re-enters the intake ports,the oil carried by this air remains in the system and serves tolubricate the piston and cylinder of the first stage.

When compressed air stored in the receiver is dispensed through thevalve 23, the pressure in the receiver drops and pressure operable means28 is rendered effective to cause sudden seating and unseating of thevalve members 35 and 31, respectively, whereby the compressor suppliescompressed air to the receiver.

While the invention has been described in connection with by-passingcompressed air from the first stage, it will be understood thatcompressed air could be bypassed from any of the other stages it sodesired.

In Figure 5, a modified compressed air system is illustrated, whereinsimilar parts have like reference numerals applied thereto. This systemillustrates the present invention applied to a single stage compressorIii having a cylinder 12, the outlet of which is connected to thereceiver 2i by a conduit l5. Air from the atmosphere is supplied to theinlet of the cylinder through the filter assembly 25 shown in Figures 2and 3, and by-passed compressed air is suppl ed to the inlet by aconduit 25' connecting the interior of the filter assembly to theconduit I5. The conduit 26 is provided with a by-pass valve 21 (Figure6) controlled by pressure operable means 28 connected by a conduit 29 tothe conduit l5 The valve 21' comprises a body havin a chamber thereinprov ded with an inlet 35' and an outlet 32' for connection in theconduit 26', and a valve seat 34 between the inlet and outlet. A valvemember 35 is retained on the valve seat by the pre sure of the airadmitted throu h the inlet and the pressure exerted by a spring 36' andis adapted to be un eated bv the stem 46' of the ressure operable means28 illustrated in Figure 6.

A check valve 15 is provided in the cond it l5 between the points atwhich the conduit: 26' and 29 are connected thereto for preventingcompressed air in the r c iver from flowing back into t compressoroutlet or into the by-pass conduit.

The head of the cylinder adjacent its intake ports is provided with atube 65 (not sho n) for distributing by-pas ed com re sed air anddirecting the same on the filter elem nt as described in connection withthe first embodiment.

In operation. while the pressure of the air in the receiver is below apredetermined value. the pre sure operable means 28 maintains the valvemember 35' in seated os tion, w ereby the air compressed in the cylinder12 flows by way of the conduit 1-5 thro gh the check val e to thereceiver. Air is admitt d to the intake of the cyl nder through thefilter assembly 25.

When a predetermined pressure has been established in the receiver, thepressure o erable means efiects unseating of the valve member 35,whereby air compressed in the cylinder is bypassed throueh the valve 2'!and is conducted by the conduit 26' to the interior of the filterassembly in the previously described manner.

From the foregoing description, it will be seen that the presentinvention provides a simple. economical and practical compressed airsystem wherein by-passed air is used for cleaning or re activating thefilter, a sudden blast of air is provided to blow out particlesaccumulated by the filter, lubricating oil picked up by the compressedair is recirculated in the system to provide lubrication for thecylinder and piston, and a portion of this lubricating oil is utilizedadvantageously for further cleaning the filter and increasing its dirtcatching ability without increasing its resistance to the flow of airtherethrough.

As various changes may be made in the form, construction and arrangementof the parts herein, without departing from the spirit and scope of theinvention and without sacrificing any of its advantages, it is to beunderstood that all matter herein is to be interpreted as illustrativeand not in any limiting sense.

It is also to be understood that the following claims are intended tocover all the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

I claim:

1. In a compressor having an intake port, the combination of a closureattached to the compressor over the intake port having an aperture foradmitting air from the exterior to the intake port, air filter meansbetween said aperture and the intake port, conduit means extending intosaid closure having an aperture adjacent said filter means for directingcompressed air against said filter means at the interior thereof, meansfor conducting compressed air from the compressor to said conduit means,and means for controlling the supply of compressed air to said lastmentioned means.

2. In a compressor having an intake port, the combination of a closuresecured to the compressor over the intake port having apertures foradmitting air from the exterior to said intake port, air filter meansbetween said apertures and the intake port, means having a plurality ofdistributing apertures for directing compressed air against said filtermeans at the interior thereof, means for conducting compressed air fromthe compressor to said directing means, and means for controlling thesupply of compressed air to said last mentioned means.

3. In a compressed air system, the combination of compressor meanshaving means for admitting air from the exterior, air filter means forsaid admitting means, a receiver, means for conducting compressed airfrom said compressor means to said receiver, means for directincompressed air against said filter means, a by-pass conduit forconducting compressed air from said conducting means to said directingmeans, valve means in said by-pass conduit for controlling the fiow ofcompressed air therethrough, and means onerable in response to thepressure in said receiver for controlling said valve means.

4. In a compressed air ystem, the combination of a compressor havingmeans for admitting air from the exterior, air filter means for saidadmitting means, a receiver, means for conducting compressed air fromsaid compressor to said receiver having a check valve therein, means fordirecting compressed air against said filter means, and a by-passconduitconnected to said conducting means between said valve and saidcompressor for conducting compressed air from said conducting means tosaid directing means.

5. In a compressed air system, the combination of a compressor havingmeans for admittin air from the exterior, air filter means for saidadmitting means, a receiver, means for conducting compressed air fromsaid compressor to said receiver having a check valve therein, means fordirecting compressed air against said filter means, a by-pass conduitconnected to said conducting means between said Valve and saidcompressor for conducting compressed air from said conducting means tosaid directing means, valve means in said by-pass conduit forcontrolling the passage of compressed air therethrough, and meansoperable in response to the pressure in said receiver for controllingsaid valve means.

6. In a compressed air system, the combination of a multistagecompressor havin means for admitting air from the exterior at the firststage thereof, air filter means for said admitting means, a receiver,means for conducting compressed air from the first stage to a subsequentstage of compression, a conduit for conducting compressed air from thelast stage of said compressor to said receiver, means for directingcompressed air against said filter means, and a by-pass conduit forconducting compressed air from said conducting means to said directingmeans.

7. In a compressed air system, the combination of a multistagecompressor having means for admitting air from the exterior at the firststage thereof, air filter means for said admitting means, a receiver,means for conducting compressed air from the first stage to a subsequentstage of compression including means for accumulating compressed air, aconduit for conducting compressed air from the last stage of saidcompressor to said receiver, means for directing compressed air againstsaid filter means, and a by-pass conduit connected to said conductingmeans between the subsequent stage of compression and said accumulatingmeans for conducting compressed air from said conducting means to saiddirecting means.

8. In a compressed air system, the combination of a multistagecompressor having means for admitting air from the exterior at the firststage thereof, air filter means for said admitting means, a receiver,means for conducting compressed air from the first stage to a subsequentstage of compression including means for accumulating compressed air, aconduit for conducting compressed air from the last stage of saidcompressor to said receiver, means for directing compressed air againstsaid filter means, a by-pass conduit connected to said conducting meansbetween the subsequent stage of compression and said accumulating meansfor conducting compressed air from said conducting means to saiddirecting means, valve means in said by-pass conduit for controlling thepassage of compressed air therethrough, and means operable in responseto the pressure in said receiver for controlling said valve means.

ALBERTUS E. SCHNIIDLIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number

